Flapper valve for an insufflation cannula assembly

ABSTRACT

A cannula assembly for use in conjunction with insufflatory surgical techniques includes a cannula, a housing mounted on one end of the cannula, and a flapper valve mounted in the housing. The flapper valve includes a valve seat which is situated at an opening formed in the housing, a valve plug which is adapted to engage the valve seat to form a substantially gas tight seal with the valve seat, and a support plate on which the valve plug is mounted and which is biased to pivot the plug into and out of engagement with the valve seat. The valve plug is movable on the support plate so as to be self-aligning with the valve seat when the plug and valve are in engagement. The valve plug is uniquely configured to include a recessed reservoir at the proximal side and surrounded by a circular ridge. The reservoir collects blood or other body fluids while the ridge is engageable by an instrument such as an endoscope which is inserted into the cannula, thus preventing the blood from covering the face of the endoscope lens.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an insufflation cannula assemblyadapted to receive a trocar, endoscope or other surgical instrument andfor use in conjunction with insufflatory surgical techniques. Moreparticularly the invention relates to a valve used in the assembly formaintaining insufflation pressure in a body cavity.

2. Description of the Prior Art

Insufflatory surgery involves filling a body cavity with a pressurizedgas to maintain the cavity under a certain predetermined pressure. Oneway of performing the surgery is by first puncturing the skin in adesired body cavity region with a needle. The needle includes a styletwhich introduces an insufflation gas into the body cavity to inflate it.

A trocar is then used to puncture the body cavity. The trocar isinserted through a cannula or sheath, which cannula partially enters thebody cavity through the incision made by the trocar. The trocar can thenbe removed from the cannula, and an elongated endoscope may be insertedthrough the cannula to view the anatomical cavity.

Various types of cannula or trocar assemblies are provided with valvesfor maintaining a certain gas pressure in the cavity when the trocar orother surgical instrument is removed from the cannula.

For example, U.S. Pat. No. 4,654,030, which issued to Frederic Moll etal., and copending U.S. application Ser. No. 920,509, filed Oct. 17,1986, disclose a trocar assembly having a cannula and employing aflapper valve to close off the cannula passage after the trocar or otherinstrument has been withdrawn.

As shown in FIG. 7 of the Moll et al. patent, the flapper valve includesa U-shaped flapper 82 and a grommet 77 formed with a central opening 78through which the trocar may be inserted or withdrawn. The flappercarries a circular pad 87, and is spring-biased so that the pad engagesgrommet 77 and forms a seal with the grommet.

Although the flapper valve disclosed in the Moll et al. patent functionssatisfactorily in most applications to maintain pressure in the bodycavity, the potential for improvement nevertheless exists.

First, the circular pad is rigidly mounted on the flapper so that itcannot move with respect to the flapper. If the pad and grommet areslightly out of alignment when the valve closes, the pad may not seatproperly on the grommet, and insufflating gas may leak from the bodycavity through the valve.

Second, the circular pad is made of a deformable material such as Tygon(TM), and is formed by a molding process. Irregularities in the pad'sgrommet-engaging surface due to shrinkage of the pad material during itsformation may provide leakage paths through the valve. Also, the padbears with considerable spring pressure on the side of the trocar whenthe trocar is inserted into the cannula through the valve. A depressionmay form in the pad's surface which may cause further leakage when thevalve closes.

Third, the circular pad is relatively flat or has a slight curvature. Itengages protruding lips 88 formed on the grommet, which lips surroundthe grommet opening 78. With this structure, the flapper valve disclosedin the Moll et al. patent provides minimal contact area between the padand the grommet, and any slight irregularity in one or the other maycause the valve to leak.

In addition to the Moll development, other improvements in such valveshave been developed. For example, in copending commonly assignedApplication No. 07/140,025, filed Dec. 31, 1987, improvements in suchvalves are disclosed which include, inter alia, the provision of aself-seating valve plug.

In all of these aforementioned developments however, there still remainsroom for improvement. For example, one difficulty which has existed withall such developments relates to the accumulation of body fluids,usually blood, on the proximal surface of the valve member when thetrocar is removed and passed by the valve members. Such accumulation offluid, while not affecting the functioning capability of the valve,nevertheless has a tendency to be transferred to other instrumentsinserted into the cannula after the trocar is removed. In particular,when an endoscope is inserted into the cannula to view the inner regionof the body cavity, the lens of the endoscope engages and actually opensthe valve. This engagement causes the lens to become smeared with theblood, thus inhibiting the surgeon's view through the endoscope. Thepresent invention relates to a flapper valve for such instruments whichpreferably includes self-seating and sealing improvements while avoidingthe aforementioned disadvantages when used in conjunction with sensitiveinstruments such as endoscopes.

SUMMARY OF THE INVENTION

A flapper valve for an insufflation cannula assembly is disclosed, thecannula assembly including a cannula defining a cannula passage and ahousing mounted on one end of the cannula and having an opening formedtherein, the flapper valve being mounted in the housing of the assembly.The flapper valve comprises a valve seat situated at the housingopening, the valve seat having an opening formed therein and being incommunication with the cannula passage and being adapted to allow asurgical instrument to pass therethrough and into the cannula passage. Avalve plug is adapted to engage the valve seat at the opening thereofand to form therewith a substantially gas tight seal, the proximal sideof the valve plug being engageable by a surgical instrument passingthrough the valve seat and into the cannula passage when the valve plugis seated in engagement with the valve seat. The valve plug isconfigured on the proximal side to prevent collection of body fluids orthe like in a manner which would transfer the body fluid to the distalface of the instrument when the instrument engages the valve plug.Biasing means is provided for biasing the valve plug into engagementwith the valve seat, and means is provided for mounting the valve plugin the housing and for pivoting the plug into and out of engagement withthe valve seat. The valve plug is preferably movable on the plugmounting means so as to be self-aligning with the valve seat openingwhen the plug and the seat are in engagement.

The present invention provides a valve for an insufflation cannulaassembly which minimizes fluid leakage through the cannula. Inparticular, a flapper valve is disclosed whose sealing membersautomatically align with each other when the valve closes to provide anenhanced gas tight seal. The sealing members of the flapper valvecontact each other over a greater surface area.

Also, an insufflation cannula assembly is disclosed for use with atrocar, endoscope or other surgical instrument, which cannula assemblyprovides negligible or no gas leakage. The present invention provides aflapper valve which is an improvement over the flapper valve disclosedin Moll et al. U.S. Pat. No. 4,654,030.

In one form of the present invention, a cannula assembly for use inconjunction with insufflatory surgical techniques includes a cannulahaving opposite open ends, a housing mounted on one end of the cannulaand having an opening formed in the housing, and a flapper valve mountedin the housing to seal the cannula passage when a surgical instrument,such as a trocar, endoscope or the like, is withdrawn from the cannula.

The flapper valve basically includes a valve seat situated at thehousing opening, a valve plug which engages the valve seat and forms asubstantially fluidtight seal with the seat, and a support plate andspring mechanism for mounting the valve plug in the housing and forpivoting the plug into and out of engagement with the valve seat. Thevalve plug includes an annular rim over the proximal face whichsurrounds a reservoir for collecting blood or other body fluids suchthat insertion of an endoscope or other instrument into the cannulacauses the lens to engage the rim. Thus smearing the lens with bloodfrom the valve plug is thereby avoided.

The valve seat has an opening formed through its thickness, whichopening is in communication with the cannula passage. The valve seat ispositioned in the housing such that its opening is co-axial with thecannula so that a surgical instrument, such as a trocar or endoscope,may be inserted through the valve seat opening and into the cannulapassage.

The valve plug is preferably mounted loosely but securely on the supportplate so that it can move radially on a surface of the support plate andalign itself with the opening formed in the valve seat when the twoengage each other. The surface of the valve plug which engages the valveseat has a frusto-conical shape so that the surface is partiallyreceived by the valve seat opening when the valve closes.

The support plate is basically a U-shaped member which extends from theradial side of an upstanding post mounted in the housing. A helicalspring mounted co-axially on the post engages the housing and thesupport plate and biases the valve plug into engagement with the valveseat when the valve plate is biased into a position immediately adjacentthe valve seat and parallel thereto, i.e. perpendicular to thelongitudinal axis of the cannula. In the preferred embodiment, thesupport plate is configured and dimensioned to engage the valve seat,particularly in the peripheral portion surrounding the opening.Simultaneously therewith, the plug engages the portion of the valve seatwhich defines the opening. A trocar or other surgical instrumentinserted through the valve seat opening will cause the valve plug topivot away from the valve seat and out of the trocar's axial path oftravel between the valve seat opening and the cannula passage, i.e.toward a direction parallel to the longitudinal axis of the cannula.

In a preferred embodiment, an insufflation cannula assembly is disclosedwhich comprises a cannula having opposite end portions, a housingmounted on one end of the cannula, the housing having an opening formedtherein. A flapper valve is mounted in the housing, the flapper valveincluding a valve seat disposed at the housing opening and having anopening formed therein to allow a surgical instrument to passtherethrough and into the cannula. The valve seat is formed of aresilient material and has an annular portion of reduced thicknessdefining the opening. The annular portion is of greater flexibility thanadjacent portions thereof due to the reduced thickness. A valve plug isadapted to engage the valve seat at the opening thereof and to form aseal with the valve seat. Means is provided for mounting the valve plugand for pivoting the valve plug into and out of engagement with thevalve seat. The valve plug is movable on the plug mounting means so asto provide the valve plug with self-seating capability to allow thevalve plug to automatically align itself with the valve seat openingwhen the plug and the valve seat are in engagement. The valve seatincludes a circular ridge at the proximal side and defines a recessedreservoir in the valve plug dimensioned and configured for collectingblood or other body fluids, whereby the self-seating capability of thevalve plug combines with the resilient annular flexible portion of thevalve seat to provide a substantially gas tight seal and insertion of anendoscope or other instrument into the valve opening and the cannulacauses the endoscope to engage the circular ridge at the proximal sideof the valve plug.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described hereinbelow withreference to the drawings wherein:

FIG. 1 is a perspective view of the cannula assembly of the presentinvention with a trocar assembly mounted thereon;

FIG. 2 is a cross-sectional view of the cannula assembly and trocarassembly shown in FIG. 1, taken along lines 2--2 of FIG. 1;

FIG. 3 is an exploded view with parts separated for illustrationpurposes, of the cannula assembly of the present invention;

FIG. 3A is a perspective view of a valve plug from the proximal side,constructed according to the present invention, illustrating a featurepertaining to the provision of an annular rim and body fluid reservoir;

FIG. 3B is a perspective view from the distal side, of an alternativeembodiment of the valve plug constructed according to the invention;

FIG. 4 is a perspective view of the cannula assembly shown in FIG. 3with the housing partially cutaway;

FIG. 5 is a rear perspective view of a portion of the cannula assemblyshowing the novel valve plug;

FIG. 6 is a partial cross-sectional view of the flapper valve used inthe cannula assembly of the present invention illustrating the novelvalve plug feature;

FIG. 7 is a top view of the cannula assembly with its housing partiallybroken away to illustrate the flapper valve and the valve plug accordingto the invention; and

FIG. 8 is an enlarged, detailed view, partially in cross-section, of aportion of the flapper valve of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIGS. 1 and 2 of the drawings, it will be seenthat a cannula assembly 2 used in connection with insufflatory surgicaltechniques basically includes a cannula 4 and a housing 6 mounted on oneend of the cannula 4. The cannula 4 is formed as an elongated sleevehaving opposite proximal and distal open ends, and thus defines acannula passage 8 in its interior. The cannula 4 may be formed from astainless steel or other rigid material.

The housing 6 of the cannula assembly is rigidly secured to the proximalend of the cannula 4. It has an open interior for mounting othercomponents of the cannula assembly, and has a rear opening 10 defined bya circular flange 12 extending inwardly of the housing, which opening 10is situated co-axially with the cannula 4. 0-ring 13 is mounted on thecannula as shown in FIG. 3, to prevent leakage between the cannula andthe housing. Additionally, the housing 6 includes a stopcock port 14into which the nozzle of stopcock 16 is inserted as shown in FIG. 4. Theport 14 is provided for passing additional insufflating gas into thebody cavity.

The cannula assembly 2, together with cannula 4 and housing 6, isadapted to receive a surgical instrument through the opening 10 in thehousing. An example of such an instrument is the trocar assembly 20shown in FIGS. 1 and 2 of the drawings, the trocar assembly beingmounted on the rear side of housing 6. Another example of suchinstruments is an endoscope which is utilized to view internal portionsof the body cavity.

The trocar assembly 20 basically includes a hand grip portion or head22, an obturator 24 mounted on the head 22 of the trocar assembly andextending outwardly from the head, and an obturator shield 26 whichhouses the obturator 24. The obturator 24 is formed with a piercing tip28 for puncturing the body cavity. A spring 30 in the head 22 of thetrocar assembly biases the shield 26 axially away from the head so thatit covers the obturator tip 28.

The trocar assembly 20 is mounted on the cannula assembly 2 so that itsobturator 24 and shield 26 are slidably received in the cannula passage8 with the obturator shield extending beyond the distal end of thecannula 4.

In operation, the distal end of the cannula/trocar assembly is placedagainst the skin at the body cavity region, and pressure is exerted onthe assembly against the skin. This pressure causes the obturator shield26 to be pushed rearwardly against the force of the spring 30 to aretracted position, thereby exposing the piercing tip 28 of theobturator. The tip enters the skin and underlying tissue with continuedpressure. Once the tip has penetrated the tissue and has entered thecavity, the force against the distal end of the shield 26 ceases and theshield is automatically moved axially forward to its extended positioncovering the tip 28 through the action of the spring 30.

A more detailed description of the trocar assembly described herein, andits operation, is provided in Moll et al. U.S. Pat. No. 4,654,030, whichis incorporated herein by reference.

As is provided in the device disclosed in the above-identified Moll etal. patent, the cannula assembly 2 of the present invention includes aflapper valve which opens to allow a surgical instrument, such as thetrocar assembly 20, to be inserted through the cannula 4, and closeswhen the surgical instrument has been withdrawn, in order to maintaingas pressure in the body cavity which has been inflated with aninsufflation gas. The flapper valve of the present invention as shown inFIG. 3 basically includes three components: a valve seat 32, a valveplug 34 which engages the valve seat 32, and a mechanism 36 for mountingthe valve plug 34 and for pivoting the plug into and out of engagementwith the valve seat 32.

As shown in FIGS. 3 through 8 of the drawings, the valve seat 32 ismounted in the circular flange 12 at the rear opening 10 formed in thehousing 6 of the cannula assembly. The seat 32 basically includes aforward portion 38 and a rearward portion 40 which are interconnectedand which define a recess 42 between them, which recess 42 receives thecircular flange 12 of the housing. The rearward portion 40 is preferablycircular, and is received in a recess 44 formed in the circular flange12.

The forward portion 38 is substantially rectangular, and has a greatertransverse width than the diameter of the circular rearward portion 40so that it extends substantially to the opposite lateral sides 46 of thehousing 6. The forward and rearward portions 38, 40 contact the sides ofthe flange over an area sufficient to prevent leakage.

The valve seat 32 includes an opening 48 formed centrally through itsthickness. The valve seat 32 is situated in the housing 6 so that itsopening 48 is co-axial with the cannula 4 and is in communication withthe cannula passage 8 through the interior of the housing; this willallow a surgical instrument, such as the trocar assembly 20 shown inFIGS. 1 and 2, or an endoscope, for example, to pass through the valveseat opening 48 and into the cannula passage 8 from the rear side of thecannula assembly housing 6.

A portion of the valve seat 32 surrounding the opening is reduced inthickness. This portion is defined by a circular recess 50 formed in therearward portion 40 of the valve seat, and a recessed groove 52 formedin the surface of the forward 38 of the valve seat and concentricallysurrounding the opening 48.

The valve seat 32 is formed from a rubber or other elastic material. Aswill be seen, because of the elasticity of the material from which it isformed and the reduced thickness of the area surrounding the opening 48,the valve seat 32 will deform to accommodate the valve plug 34 andthereby conform to the shape of the valve plug 34 when the two engageeach other, with substantial areas of the two being in contact so as toform a substantially gas tight seal. Also, the reduced thickness portionat 50 and 52 surrounding the valve seat opening 48 allows the valve seat32 to expand and closely engage the obturator shield 26 of the trocarassembly 20 or other surgical instrument inserted in the cannulaassembly, and to prevent fluid from escaping from the body cavity.

As mentioned previously, the flapper valve also includes a mechanism 36for mounting the valve plug 34 and for pivoting the valve plug into andout of engagement with the valve seat 32. As shown in FIG. 3 of thedrawings, such a mechanism includes a support plate 54 which ispreferably U-shaped. The support plate 54 extends outwardly from aradial side of an upstanding post 56 mounted in the housing of thecannula assembly.

A tensioned helical spring 58 is co-axially mounted on the post 56, andincludes two ends 60, 62. One end 60 bears against a side 46 of thecannula housing 6, and the other end 62 bears against the rear side 63of the support plate below a tab 64 extending outwardly from the rearside, which tab 64 keeps the spring end in place. The spring 58 biasesthe support plate 54 such that the valve plug 34 mounted on the platewill engage the valve seat 32 to effect a gas tight seal when thesupport plate 54 is biased to the position shown in FIG. 6, i.e.parallel to and immediately adjacent the support plate 54.

When a trocar or other surgical instrument (i.e., an endoscope) isinserted through the valve seat opening 48 into the housing 6 of thecannula assembly, it will engage the valve plug 34 and cause the supportplate 54 to pivot against the force of the spring 58 towards the side 46of the housing so that the valve plug 34 is out of engagement with thevalve seat 32 as shown in FIG. 7. In this position, the orientation ofthe support plate is near a direction generally parallel to thelongitudinal axis of the cannula. This opens the valve and allows thesurgical instrument to be inserted through the interior of the cannulaassembly housing 6 and into the cannula 4. When the trocar or endoscopeis withdrawn, the support plate 54 is spring biased to pivot so that thevalve plug 34 will automatically engage the valve seat 32, therebyclosing the valve.

Referring now to FIG. 3A, a major feature of the present invention isillustrated. This Figure is a perspective view of the valve plug 34 ofthe present invention. Valve plug 34 is shown separated from the supportplate 54 for convenience of illustration. In FIG. 3A the valve plug 34is configured to include at the proximal face, a recessed reservoir 35whose outer boundary is defined by annular rim 36 as shown. The recessedreservoir is provided to collect any body fluids, i.e. blood, etc.,which would normally tend to accumulate on the proximal side of the plugwhen trocar 16 is removed from the cannula after the body cavity hasbeen pierced. Passage of the trocar by the flapper valve would naturallycause the valve plug to be somewhat covered with the fluid.

The collection of such fluid within the reservoir 35 of the presentvalve structure thus avoids accumulation of fluid on a proximal outersurface of the valve plug 34. Moreover, the presence of the rim 36 onthe proximal side of the valve plug 34 thus presents a clean rim at alltimes to any instrument inserted into the cannula, rather than a surfacecovered with blood. Hence, when the trocar is removed and the surgeoninserts another instrument such as an endoscope 31 (see FIG. 3A) havinga clear lens 33 at the distal end, the engagement of the lens 33 withthe rim 36 of the plug 34 avoids transfer of the body fluid to the faceof the endoscope as would otherwise occur with prior art instruments.Thus the presence of the reservoir 35 and rim 36 tend to prevent theaccumulation of blood or other body fluids on the proximal side of theplug where the lens 33 engages the plug 34. The absence of such fluidcollection makes it possible to insert the endoscope without theaforementioned adverse affects.

Turning once again to FIG. 4 in conjunction with FIGS. 1 and 7, a lever66 is provided on the outside of the housing 6. The lever 66 is mountedto the upstanding post 56 and pivots with the post when the supportplate 54 is pivoted. In addition to providing visual indication of theposition of the support plate 54, lever 66 is provided for the surgeonto manipulate so that the valve can be manually opened to desufflate thebody cavity. To ensure fluid tightness, an 0-ring 68 is mounted on thepost between the spring 58 and the lever 66.

The support plate 54 also has an opening 70 extending entirelytherethrough as shown, that is, between its rear and front sides 63, 65.As will be seen, the opening 70 is provided for mounting the valve plug34 to the support plate.

As can be seen in FIGS. 3A and 8, the valve plug 34 of the flapper valvebasically includes a recessed reservoir 35 having a front face 72 (shownin phantom lines) surrounded by rim 36, and a rear face 74 opposite thefront face. The outer portion 76 of the front face is formed with aconical shape, and more preferably, a frusto-conical shape. Theconically-shaped portion 76 of the valve plug is preferably slopedinwardly on its sides at an angle "A" of about 30°.

As shown in FIGS. 3 and 3A, the recessed face 72 of the reservoir 35 ofvalve plug 34 is surrounded by a conical or frusto-conical face 76. Aflange 78 which surrounds the conically-shaped portion 76 and extendsradially outward as shown acts to ensure that the tip of shield 26 ofthe trocar assembly, or lens 33 of endoscope 31, or other surgicalinstrument which may be inserted, is guided into the cannula 4 and doesnot momentarily get hung up at the joint formed by valve plug 34 andsupport plate 54 as the support plate 54 and plug 34 pivot inwardly.

As mentioned previously, the valve plug 34 is mounted on the supportplate 54 and pivots with the support plate into and out of engagementwith the valve seat 32. One of the important features of the flappervalve of the present invention which distinguishes it from the valveemployed in the trocar disclosed in U.S. Pat. No. 4,654,030 (Moll etal.) and others, is that the valve plug 34 is loosely but securelymounted on the support plate 54 so that it can move radially to acertain extent on the front face of the support plate. The ability ofthe plug 34 to move with respect to the support plate 54 and theparticular shape of the valve plug (i.e., conical or frusto-conical)provide the valve plug with a self-seating capability which allows it toautomatically align itself with the valve seat 32 when the two engage.This capability is further enhanced by the provision of recess 35 andannular rim 36 which is engaged by the surgical instruments.

A stem portion 80 extends outwardly from the rear face 74 of the valveplug 34. As will be seen, the stem portion 80 is provided for mountingthe valve plug 34 to the support plate 54, and for providing the valveplug with a degree of radial movement on the front side of the supportplate.

The stem portion 80 includes a free end on which is mounted a retaininghead 82. Alternatively, the retaining head 82 may form the free end ofthe stem portion 80. The retaining head 82 in its preferred form is alsofrusto-conically shaped with sides that converge in a direction awayfrom the rear side 63 of the support plate, preferably sloping inwardlyat an angle "B" of about 20° as shown in FIG. 8.

The valve plug 34 is mounted on the support plate 54 with itsconically-shaped front face 72 (and recessed reservoir 35) and itsretaining head 82 disposed on opposite front and rear sides 65, 63 ofthe support plate, respectively, and with its stem portion 80 receivedwithin the support plate opening 70.

The retaining head 82 is dimensioned to be oversized, that is, with adiameter that is greater than that of the support plate opening 70, tosecurely connect the valve plug 34 to the support plate 54. In thepreferred embodiment, the stem portion 80 of the valve plug is formedwith a diameter that is less than that of the support plate opening 70.Thus, when mounted on the support plate 54, the valve plug 34 is free tomove in any radial direction on the front side 65 of the support plate,and is limited in its radial movement by the difference between thediameters of the support plate opening 70 and the stem portion 80.

For example, if the support plate opening 70 is formed with a diameterof 0.127 inches and the valve plug stem portion 80 is formed with adiameter of 0.095 inches, then the valve plug will be able to travel0.016 inches from the center of the support plate opening in any radialdirection.

The valve plug 34 is thus free to "float" on the surface of the supportplate 54 in any radial direction, and to align itself with the centralopening 48 formed in the valve seat 32. When the valve closes, theengagement of the valve seat 32 with the frusto-conical front face ofthe valve plug 34 forces the valve plug into proper alignment with thevalve seat to effect a gas tight seal.

The rear face 74 of the valve plug 34 is also formed with a recessedcentral portion 84 concentrically surrounding the stem 80. This recessedcentral portion 84 is provided basically for two reasons. First, itprovides the plug with less surface area on its rear face 73 to contactthe front side 65 of the support plate. This reduces the drag orfriction between the two and allows free movement of the valve plug 34on the support plate 54.

Second, if desired, the recessed central portion 84 may serve to receivea silicone grease or other lubricant to lubricate the interface betweenthe valve plug and the support plate, which also minimizes frictionbetween the two.

An alternative embodiment of the plug 34 is shown in FIG. 3B wherein therecessed portion 74B is annular and peripheral and surrounds a centralraised portion 84B. This embodiment also provides the same reducedfriction and lubrication advantages as specified above in connectionwith the embodiment of FIG. 3.

If desired, the front face 72 of the valve plug 34 may be formed from amaterial such as plastic, aluminum, stainless steel or the like. Theretaining head 82 may be formed from the same or other material as thefront face 72 of the valve plug and joined to the end of stem portion 80after the stem portion has been mounted in the support plate opening 70,or may be formed from a relatively elastic material and force-fittedthrough plate opening 70. The retaining head 82, formed of resilientmaterial, can compress and then expand after its insertion through thesupport plate opening, and thereby return to an intentionalinterference.

The valve seat 32, being molded of rubber or other elastic material,conforms by stretching and compressing to the shape of the valve plug 34when the valve plug is wedged in the valve seat opening 48. Thus, thevalve seat surrounding the opening 48 can engage the valve plug 34 oversubstantially all of its entire thickness to form an effective gas tightseal.

The valve seat may be mounted in a circular recess 86 (see FIG. 8)formed in the front side 65 of the support plate 54, the diameter of thecircular recess 86 being made sufficiently large so as not to limit theradial movement of the valve plug on the support plate.

The flapper valve of the present invention provides an enhanced gastight seal by its capability of being self-seating. More significantly,as noted, the recessed reservoir at the proximal side of the plugfacilitates collection of blood or other body fluids while the annularrim surrounding the reservoir can be engaged by a sensitive instrumentsuch as an endoscope without smearing the lens. In addition, thefrusto-conical shape of the valve plug 34 and its ability to "float" onthe support plate 54 allow it to come into proper alignment with thevalve seat 32 when the two engage. Furthermore, the configuration andelasticity of the valve seat 32 and the particular shape of the valveplug 34 permit the two to contact each other over a greater surfacearea, thus ensuring an effective seal.

What is claimed is:
 1. A flapper valve for an insufflation cannulaassembly, the cannula assembly including a cannula defining a cannulapassage and a housing mounted on one end of the cannula and having anopening formed therein, the flapper valve being mounted in the housingof the assembly, the flapper valve comprising:a valve seat situated atthe housing opening, said valve seat having an opening formed thereinand being in communication with said cannula passage and being adaptedto allow a surgical instrument to pass therethrough and into the cannulapassage; a valve plug adapted to engage the valve seat at the openingthereof and to form therewith a substantially gas tight seal, theproximal side of said valve plug being engageable by a surgicalinstrument passing through said valve seat and into the cannula passagewhen the valve plug is seated in engagement with the valve seat, saidvalve plug having means on the proximal side to prevent collection ofbody fluids in a manner which would transfer body fluid to the distalface of the instrument when the instrument engages said valve plug;means for mounting said valve plug in said housing and for pivoting saidplug into and out of engagement with said valve seat; and biasing meansfor biasing said valve plug into engagement with said valve seat.
 2. Aflapper valve as defined in claim 1, wherein said valve plug has afrusto-conically shaped front face which engages said valve seat.
 3. Aflapper valve as defined by claim 1, wherein said valve plug includes afront face which engages the valve seat, and a rear face opposite thefront face, and further includes a stem portion extending outwardlydistally from the rear face thereof; and wherein the plug mounting meansincludes a support plate, the support plate having an opening formedtherein, said opening being adapted to receive the stem portion of saidvalve plug to allow said plug to be mounted on the surface of saidplate, the diameter of said support plate opening being greater than thediameter of said plug stem portion; and wherein said flapper valvefurther includes means for securing the stem portion within said supportplate opening, and an annular ridge on the proximal side of said valveplug surrounding a recessed reservoir portion dimensioned to receive andaccumulate body fluids such that when the surgical instrument isinserted through said valve seat opening so as to engage said valveplug, the distal surface portion of the instrument engages said annularridge and transfer of body fluid from the proximal side of said plug tothe distal surface of the instrument is thereby avoided.
 4. A flappervalve as defined by claim 3, wherein said stem portion of said valveplug includes a free end; and wherein said plug further includes aretaining head, said retaining head being mounted on the free end ofsaid plug stem portion, said retaining head having a greater diameterthan that of said support plate opening.
 5. A flapper valve as definedin claim 1, wherein said valve plug includes a front face which engagessaid valve seat, and a rear face opposite said front face, and furtherincludes a stem portion extending outwardly from the rear face thereof,the stem portion having a free end, and a retaining head mounted on thefree end of said plug stem portion; and wherein said support plate hastwo opposite sides and defines an opening therethrough, said openingreceiving said valve plug stem portion such that said retaining head andsaid front face are disposed on opposite sides of said support plate,the diameter of said support plate opening being greater than that ofsaid stem portion and being less than that of the retaining head.
 6. Aflapper valve as defined by claim 1, wherein the front face of saidvalve plug is formed of a substantially inelastic material.
 7. A flappervalve as defined by claim 1, wherein said valve seat is formed of anelastic material.
 8. A flapper valve as defined by claim 1, wherein saidvalve plug includes a front face having a conically-shaped portion and aflange surrounding said conically-shaped portion, and further includes arear face opposite the front face, the front face being configured,dimensioned and adapted to engage the valve seat.
 9. A flapper valve asdefined by claim 8, wherein the rear face of said valve plug includes aperipheral annular recessed portion surrounding a central portionextending distally of said recessed portion.
 10. A flapper valve asdefined by claim 8, wherein the rear face of said valve plug includes anannular raised portion surrounding a central raised portion.
 11. Aflapper valve as defined by claim 1, wherein said plug mounting meansincludes a support plate, said support plate being pivotally mounted insaid housing and having said valve plug mounted thereon, and beingbiased to pivot said valve plug into engagement with said valve seat.12. A flapper valve as defined by claim 1, wherein said valve plugincludes a stem portion extending from a surface thereof, said stemportion being loosely received in an opening formed in said plugmounting means.
 13. A flapper valve as defined by claim 1, wherein thevalve seat is situated in the housing such that said valve seat openingis co-axial with the cannula.
 14. A flapper valve as defined by claim 1,wherein the proximal side of said valve plug includes a conically orfrusto-conically shaped surface which terminates at the proximal endwith a circular raised ridge, said circular ridge surrounding anddefining a recessed reservoir dimensioned and configured to collect bodyfluids, whereby said circular ridge is engaged by any instrumentinserted into said valve seat opening and the cannula.
 15. A flappervalve as defined by claim 1, wherein said valve plug is movable on saidplug mounting means so as to be self-aligning with said valve seatopening when said plug and said seat are in engagement.
 16. A flappervalve for an insufflation cannula assembly, the cannula assemblyincluding a cannula defining a cannula passage and a housing mounted onone end of the cannula and having an opening formed therein, the flappervalve being mounted in the housing of the assembly, the flapper valvecomprising:a valve seat formed of a resilient material and situated atthe housing opening, said valve seat having an opening formed thereinsaid valve seat opening being in communication with the cannula passageand being adapted to allow a surgical instrument to pass therethroughand into the cannula passage, said valve seat having an annular portionof reduced thickness defining said opening, said annular portion therebybeing of greater flexibility than adjacent portions thereof; a valveplug having a conically or frusto-conically shaped front face whichengages said valve seat, said valve plug being adapted to engage saidvalve seat at said opening thereof and to form a seal therewith, saidplug further having a circular endless ridge at the proximal enddefining a recessed reservoir for collection of blood or other bodyfluids, said ridge being engageable by an instrument inserted into saidvalve seat opening and the cannula when the valve plug is seated againstsaid valve seat; means for mounting said valve plug in the housing andfor pivoting said valve plug into and out of engagement with saidannular portion of said valve seat; and biasing means for biasing saidvalve plug into engagement with said valve seat.
 17. A flapper valve asdefined by claim 16, wherein said valve plug is movable on said plugmounting means sufficient to provide said valve plug with self-seatingcapability to thereby allow said valve plug to align itself with saidvalve seat when said valve plug and said valve seat are in engagement,whereby said self-seating capability of said valve plug combines withsaid resilient annular flexible portion of said valve seat to provide asubstantially gas tight seal.
 18. An insufflation cannula assembly whichcomprises:a cannula having opposite end portions; a housing mounted onone end of the cannula, said housing having an opening formed therein;and flapper valve means mounted in the housing, said flapper valve meansincluding a valve seat disposed at the housing opening and having anopening formed therein to allow a surgical instrument to passtherethrough and into the cannula, said valve seat formed of a resilientmaterial and having an annular portion of reduced thickness definingsaid opening, said annular portion being of greater flexibility thanadjacent portions thereof due to said reduced thickness, a valve plugadapted to engage said valve seat at the opening thereof and to form aseal with said valve seat, and means for mounting said valve plug andfor pivoting said valve plug into and out of engagement with said valveseat, said valve plug including a circular ridge at the proximal sideand defining a recessed reservoir in said valve plug dimensioned andconfigured for collecting blood or other body fluids, whereby saidresilient annular flexible portion of said valve seat provides asubstantially gas tight seal and insertion of an endoscope or otherinstrument into said valve opening and said cannula causes the endoscopeto engage said circular ridge at the proximal side of said valve plug.19. An insufflation cannula assembly as defined by claim 18, whereinsaid valve plug is movable on said plug mounting means so as to providesaid valve plug with self-seating capability to allow said valve plug tobe automatically self-aligning with said valve seat opening when saidplug and said valve seat are in engagement.
 20. An insufflation cannulaassembly as defined by claim 19, wherein said plug mounting meansincludes a support plate having an opening formed therein and said plugincludes a stem portion of diameter less than said plate opening topermit lateral movement of said plug on said plate when said stemportion is positioned within said plate opening.
 21. A flapper valve foran insufflation cannula assembly wherein the cannula assembly includes acannula defining a cannula passage and a housing mounted at one end ofthe cannula and having an opening formed therein, the flapper valvebeing mounted in the housing of the assembly, comprising:a valve seatsituated at the housing opening, said valve seat having an openingformed therein and being in communication with the cannula passage andbeing adapted to allow a surgical instrument therethrough and into thecannula passage; a valve plate pivotally mounted in said housing, saidvalve plate including means for obstructing said opening of said valveseat when said valve plate is pivoted to a first position immediatelyadjacent said valve seat and oriented therewith, said valve openingobstructing means having means on the proximal side thereof to preventcollection of body fluids in a manner which would transfer the bodyfluid to the distal face of an instrument when the instrument engagessaid valve opening obstructing means; biasing means for biasing saidvalve plate into said first position immediately adjacent said valveseat.
 22. An insufflation cannula assembly as defined by claim 21,wherein said first position of said valve plate is generally parallel tosaid valve seat and generally perpendicular to the longitudinal axis ofthe cannula.
 23. An insufflation cannula assembly as defined by claim22, wherein said valve plate is pivotable to a position generally towarda direction in alignment with the longitudinal axis of the cannula whenthe instrument is passed through the housing.
 24. An insufflationcannula assembly, which comprises:a cannula, the cannula having oppositeends; a housing mounted on one end of the cannula, the housing having anopening formed therein; and a flapper valve mounted in the housing, saidflapper valve comprising a valve seat disposed at the housing openingand having an opening formed therein to allow a surgical instrument topass therethrough and into the cannula, a valve plug adapted to engagethe valve seat at the opening thereof and to form with the valve seat asubstantially fluidtight seal, said valve plug being having means on theproximal side to prevent collection of body fluids in a manner whichwould transfer the body fluid to the distal face of an instrument whenan instrument engages said valve plug, and means for mounting the valveplug and for pivoting the plug into and out of engagement with the valveseat, the valve plug being movable on the plug mounting means so as tobe self-aligning with the valve seat opening when the plug and valveseat are in engagement.
 25. A flapper valve for an insufflation cannulaassembly, the cannula assembly including a cannula defining a cannulapassage and a housing mounted at one end of the cannula and having anopening formed therein, the flapper valve being mounted in the housingof the assembly, comprising:a valve seat situated at the housingopening, said valve seat having an opening formed therein and being incommunication with said cannula passage and being adapted to allow asurgical instrument to pass therethrough and into the cannula passage; avalve plug adapted to engage the valve seat at the opening thereof andto form therewith a substantially gas tight seal, the proximal side ofsaid valve plug being engageable by a surgical instrument passingthrough said valve seat and into the cannula passage when the valve plugis seated in engagement with the valve seat; means for mounting saidvalve plug in said housing an for pivoting said plug into and out ofengagement with said valve seat; means for biasing said valve plug intoengagement with said valve seat; and means on the proximal side of saidvalve plug for collecting body fluids which accumulate on said proximalside and to prevent transfer of fluid to a distal surface of theinstrument when the instrument engages said valve plug.
 26. A flappervalve as defined by claim 25 wherein said body fluid collectively meanscomprises an annular ridge defining a recessed reservoir portiondimensioned and configured to receive and accumulate body fluids suchthat upon insertion of the instrument into said cannula assembly thedistal surface of the instrument engages said annular ridge and transferof body fluid from said recessed reservoir portion to the distal surfaceof the instrument is thereby avoided.